In the cultivation of hops support structures or trellises are used which consist of stakes anchored in the ground and connected by longitudinal, that is, generally horizontally extending wires. To twine the hop vines, guide or riser wires are provided which extend parallel to each other and in spaced relationship and generally accordingly are a direction across to the horizontal wires of the support structure. One end of the vertical wires is pegged in the ground, while the other end is connected with the horizontal main wires.
The hop plants twine around these riser wires during their growth until they reach the longitudinal wires which extend at a height of 7 to 8 meters above ground, and then climb over the horizontal wires and further branch out during their growth. After a harvest the support structure as such remains preserved. However, the plants with the riser wires are torn down at the time of the harvest and moved to the picking machine. The unused remainders of the plants are then destroyed together with the riser wires, for instance by chopping or burning.
The securing of the riser or vertical wires is generally effected from a hydraulically lifted staging disposed on a vehicle which passes through the rows of plants. It is carried out accordingly several meters above the ground. It stands to reason that the work on the movable staging because of the uneven ground which must be traversed by the vehicle is difficult and requires skill. This, however, is necessary to connect the riser wires to the main horizontal wires. Black lacquered iron riser wires have long been used for the guiding up of the plants. The free end of the riser wire which is opposite the end peg in the ground is connected with the horizontal wire by coiling around the same or spiral coiling of the end of the riser wires about itself after bending it back. These black iron wires have particularly the shortcoming that in spite of the lacquer coating they have a tendency to corrode at the surface or, particularly at the places of friction, that is including the places where they are fastened, they have a tendency to rust throughout their cross section. This surface or through-rusting can also occur if the total storage supply is not used up for one harvest by the farmer. This occurs particularly since the wire normally is stored in a condition coiled around big rolls. It frequently is stored in a less than proper manner. If the surface corrosion results in an untimely through-corrosion or if the surface corroded wire tears because of the weight of the plant, the vines drop down prior to the harvest and must be twined again individually in a time-consuming manner. Besides, the iron wires require a strength of about 1.2 mm diameter and therefore are expensive and heavy.
It has also been proposed to replace the comparatively expensive easily corrodable black iron wire by a yarn of plastic material or a rope of the same material which consists of a multiplicity of slightly twisted monofilaments. These riser yarns of plastic material, however, have the shortcoming when compared with the iron wires that they are difficult to tie because of the lack of flexibility and the smoothness of their surface since the tying has to be performed at the place of use. Besides the fastening to the horizontal wire comes off easily when the vertical wire is subjected to a tensile stress.
To counter this shortcoming the German Gebrauchsmuster No. 7,216,343 (not published in print) proposes to use definite performed lengths of yarns which correspond to the required length of each individual riser wire and to provide them with a device for securing them to the other wire in the form of a welded-on or sprayed-on reinforcing body which prevents that the fast end escapes from the loop or knot.
Riser yarns of this type are fairly difficult to make since the yarn furnished by the supplier in rolls or coils must be sprayed around its surface with a plastic material at spaced internals. Multiple molds can be used for this purpose only in a limited way. Also, the tearing down of the wire at the time of the harvest or immediately thereafter as wanted by the farmers could not always be guaranteed.
German Gebrauchsmuster No. 7,304,350 which likewise has not been published in print, proposes a fastener for the riser wires consisting of a plastic monofilament which consists of a hook-shaped body of plastic material. The fastening shank of the body has an aperture which is adapted to the diameter of a terminal knot of a slightly twisted guide cord. In this manner a self-jamming of the end of the cord which is formed with a knot in the slot of the hook should be accomplished.
However, apart from the fact that the cords could not be torn definitely at the time of the harvest, it was also very difficult for the operator standing on the staging to thread the ends of the rope into the slots of the hook. As a consequence, the hook had to be taken off after each harvest and had to be supplied with a new cord prior to the next harvest in order to suspend it again from the horizontal wires.
It is also particularly difficult to chop the multiplicity of thin filaments which form the slightly twisted yarns of the riser wire after the harvest together with the harvested plants. They have a tendency to get jammed in the chopper knife, to coil around the chopper shaft and thus to cause an overheating which results in their burning up with the formation of melt lumps if the chopping machine is not totally disabled and stopped.
A long time ago it has also been proposed to suspend S-shaped iron hooks similar to so-called butcher hooks from the horizontal main wires and to fasten the riser wires in the lower curved end of the hook in a specific manner. This was accomplished by coiling around the lower shank of the hook or to hook them by means of a so-called "cuckoo" from a wire loop. If after, or at the time of the harvest, there was a pull at the riser wires, the S-shaped comparatively large and widely curved hooks frequently were hurled up, and detached from the horizontal wires caused injury to the farmer.
In spite of the many proposals and suggestions in this area, so far no satisfactory riser wire system has been found which meets the requirements of the farmers.
It is therefore an object of the invention to provide for a riser wire system for hop vines which combines the advantages of the iron wire with the wires made of plastic materials but does not involve the shortcomings of the old systems which have been described above. Besides, it should help to save time and expense and accordingly result in better harvest yields.